Answer:
Somebody who is busy with work - an occupied mind as opposed to an idle one - doesn't have time to think about sinning or doing any evil.
Somebody that has an idle mind has too much time on their hands and think-up and falsely imagine problems in their life that do not really exist. However, a busy mind at work, at school or both will stay occupied and will go about life in a happy typical manner, NOT falsely imagining problems in their life.
A society that had increasing free time and increasing knowledge also had time to think.. learn and debate all aspects of life. Such as religion.. and man's existence. When an educated and knowledgeable society rises, the ability of those who would seek to control them - such as governments & religious groups/cults - they lose the ability to do so.